Recent research investigating childhood conduct problems (CP) has emphasized the role of examining callous/unemotional traits (CU). CU traits refer to a shallow range of emotions including low empathy, a lack of guilt or remorse, and a lack of caring about behavioral performance. Over a decade's worth of research has shown that children with CP and high levels of CU (CP/CU) differ in meaningful ways from children with CP with low levels of CU (CP-only). Although CU traits are indicative of severe CP, it is important to note that the nature of the difference is not as simple as concluding that children with CP/CU are always worse than children with CP-only. For example, children with CP/CU experience less impairment than those with CP-only in other areas of functioning including social cognition and verbal intelligence. In addition, children with CP/CU exhibit impairments unique to their condition (that are not related to CP-only) including deficits in identifying fear and sad emotions and deficits in learning from punishment. Perhaps not surprisingly then, antisocial behaviors among children with CP/CU are less strongly associated with factors related to CP (e.g., ineffective parenting; low verbal IQ). This suggests that different mechanisms underlie antisocial behaviors in children with CP such that a unique mechanism may underlie antisocial behaviors in children with CP and high CU traits. CU-related mechanisms in childhood are an important area to examine given that CU traits indicate a severe form of childhood CP, and yet represent a gap in the literature. Filling this gap has great potential to inform assessment methods for CP and contribute to novel treatments aimed at addressing the unique impairments associated with severe antisocial behavior in these children. The current study proposes to examine a cognitive mechanism-response modulation (RM)-that is influential in understanding CU-related antisocial behavior in adults and adolescents. RM suggests that individuals with CP/CU are less able to shift their attentional focus away from information central to their immediate goal and towards information that is important yet peripheral to this goal. Because attending to peripheral information is crucial in modulating between behaviors to achieve a goal in the moment, individuals with CP/CU-who exhibit a less efficient RM process-are less able to modify their ongoing and goal-directed behaviors (including antisocial behaviors). This impaired process has direct implications for their severe antisocial behavior in the moment and their severe maladjustment over time. No research has examined RM in children with CP/CU. The primary aim of the proposed study is to examine the relationship between RM and CU in children with CP/ADHD. To address this aim, 66 children with CP/ADHD (ages 7-12) will complete a number of cognitive lab tasks that have demonstrated validity in measuring RM in adults and adolescents. The efficiency of the RM process will be assessed using CP and CU as predictors of RM. Not only will the current study inform the childhood CP/CU literature, but it will also extend the RM literature.